Thermostatically-controlled electric switch



1,639,655 Aug.23, 1927. c. M. HOLLEY THERMOSTATICALLY CONTROLLED ELECTRIC SWITCH Filed Feb.23. 1922 INVENTOR. f/arevce /V. Holley.

.4 XV/M A TTORNEY.

Patented Aug. 23, 1927.

UNITED STATES PATENT OFFICE.

CLARENCE M. HOLLEY, F HIGHLAND PARK, MICHIGAN, ASSIG-NOR, BY ME SNE AS- SIGNMENTS, TO THE HOOVER COMPANY, OF NORTH CANTON, OHIO, A CORPORA- TIOIN' OF OHIO.

THERMOSTATICALLY-CONTROLLED ELECTRIC SWITCH.

Application filed February 23, 1922. Serial No. 538,726.

This invention relates to thermostatically controlled electric" switches, and its object is to provide an electric switch for making and breaking the circuit of an apparatus to I be energized, as for instance an electric motor, the time of the making or breaking of the circuit being controlled through variations in temperature. It is to be understood that the switch may be adapted for use wherever it is desired to control the making or breaking of an electric circuit by variation in temperature and one such use of the in vention is in conjunction with an artificial refrigerating plant in which the temperature of the atmosphere of the compartment being cooled is utilized to automatically maintain the compartment at a temperature varying between certain high and low limits as hereafter will more fully appear. I am familiar with various devices utilized for the performance of this function but the apparatus heretofore used for this purpose I is ordinarily .quite expensive, very delicate slow and gradual that a good contact is,

oftentimes not made and oftentimes the circuit is not "actually closed although the switch arm has been moved to closed position. Anobject of this invention is to provide a switch arm that forcibly makes a contact producing a jar or hammer like blow upon the contact being made by the switch arm, and further the object is to provide a switch arm that requires but very slight actuation through the expansion or contrac-.

tion of the bi-metallic element to produce the complete throw of theswitch arm. I have accomplished this in a novel structure in which the switch arm is weighted and so delicacy in its construction and am able to provide a thermostatic control for the electric circuit operating within a very small temperature range whereas devices heretofore used for that purpose require a temperature change of something like fifteen or more degrees F. to affect operation. These and other objects and the various novel featuresof the invention are hereinafter more fully described and claimed, and the preferred form of construction of a thermostatically controlled switch embodying my invention is shown in the accompanying drawings in which 1 Fig. 1 is a longitudinal section of the thermostatic switch showing the controlling bi-metallic element.

Fig. 2 is an elevationshowing the thermostatic switch and manner of mounting.

In artificial refrigerating apparatus an electric motor is ordinarily utilized for the compression of the refrigerant fluid which 1s" expanded in an expansmn c011 positioned to influence the temperature of a storage compartment. If the motor continues to run for any considerable period of time the temperature of the compartment would fall below that required to prevent destruction of the food or other matter contained therein. Therefore a thermostatic switch is em ployed to control the motor circuit to break the motor circuit upon attainment of a certain low degreeof temperature in the compartment andto make or close the motor. circuit and start operation of the apparatus upon attainment of a certain predetermined high degree of temperature in the storage compartment. For this purpose I employ a. thermostatic switch element shown in Figs. 1 and 2. This switch element, as I prefer to make it, consists of a rod or shaft 1 supported in any convenient way, as for instance by a member 2 which may be a wall of the storage compartment or a block supiii ported on the said wall, the shaft extending through this block or member 2 and fixedly secured in place and held from rotation. The opposite end of the rod is threaded and on said threaded part is a head 3 which pro-' vides an anchor for a thermostatic element 4. This thermostatic element is the usual bimetallic element commonly in use which is made in the form of a helix for the purpose of securing an extreme length in as small a space as is possible and secure the maximum expansion and contraction of the device. One end of this thermostatic element is secured by means of a screw 5 to the hub of this member 3 and the opposite end is secured in the same manner to the hub of the case 6 containing the switch member 7. The case may be made of two similar parts, the inner hubs of which are threaded and a tube 17 threaded thereon as indicated in Fig. 1 to hold the two parts together. A paper gasket is preferably provided between the meeting edges of the two parts to seal the same and prevent introduction of moisture into the case. The switch elen'icnt is shown more clearly in Fig. 2 and consists of a head 8 and a loop portion 9 open at the center passing around the huboi the two parts of the case and pivotally supported in a yoke 10 at thebottom of the case. Practically the entire weight of the switch arm is above the pivot point and it is therefore top heavy or unstable. It is intended that this case shall normally stand approximately as shown in Fig. 2 with the pivot point 1]. on a vertical line passing through the center of the case, but it is to be noted that a very slight rotation of the case on the shaft in one direction or the other immediately unbalances the top heavy switch arm causing it to fall to the right or to the left. This is a particular feature of this invention in that by mounting the switch case to turn about the axis of the shaft 1 and pivoting the switch member or arm at 'l' at a point below that axis, the slightest movement of the switch body unbalances the switch arm causing the switch arm to fall by gravity in one direction or the other into contact with the terminal 12 or 13 as the case may be. These terminals are mounted in one side of the case as indi 'atcd more particularly in Fig. 2 and consists of a flatmember having an upturned end 14 in each instance against which screws 15 supported at the head of the switch arm may contact. Each screw is threaded through a lug of the arm and is provided with a lock nut iii to lock the screw in its adjusted position. The two halves of the case 7 are connected together by a threaded union 17 as will be understood from Fig. 1 and therefore one side of the case may be unscrewed from the union to expose the switch arm permit adjustmerit of the contacts without disassembly of the case from the shaft and therefore 1 prefer to have the electrical connections in one of the said halves of the case.

By temperature change the bi-mctallic element 4 will expand or contract depending upon whether the temperature increases or decreases and in expanding will tend to elongate longitudinally of the shaft and also will tend to turn about the shaft; Therefore the two halves of the switch case 6 are provided with a tapered aperture of least diameter at the point of contact of the two halves at the center. The contact of the case on the shaft therefore is practically a line contact at the center of the case and this will enable the case to vary in angular relation to the shaft and permits great freedom of movement either in turning or slidinp on the shaft and also prevents the case from binding on the shaft. This structural feature is desirable in View of the fact that the pressure exerted on the case is at one side thereof in the construction here shown. As heretofore stated the member El is threaded on the end of the shaft and this may be turned to permit an adjustment of the position of the case 6 rotatively of the shaft and this adjustment. it will be observed would onable the case to be set with the point ll to the right or to the left of a vertical line passing through the center of the shaft 1 and this would require a greater movement oi the case to cause contact oi the switch arm with the contacts 12 or 13. The temperature range at which this device operates may therefore be adjusted by the turning oi this member 3. Preferably a spring: disc 18 is used that is concavoronve); in form and a nut 19 at the outer end of the shaft may be turned down to cause pressure of the spring 18 on the member 3 to prevent accidental displacement of the member so that when the member has been set it retains its set position. In this connection it is to be noted that the shaft 1 and member 3 are held stationary, and that it is only the case 6 that may be turned by the elongation or contraction of the bi-mctallic element 4.

From the foregoing description it is believed evident that a simple and ellicicnt apparatus is provided for controlling a motor circuit or circuit to other electrical apparatus which is required to be closed or opened to correspond with a predetermined temperature change. By the particular arrangement of the thermostatic element, switch arm and case therefor and pivoting of the switch arm at a point below the point about which the case may turn the ellect of the expansion or contraction of the thermostatic element is multiplied so that very little turning movement of the thermostatic element imbalances the switch arm which thereupon moves the remaining distance by gravity to one or the other of the contacts. It is further to be noted that the switch case is mounted to move freely on its shaft and by this arrangement and use therewith of an unstable switch arm, no determined strain is imposed upon the bi-metallic element and therefore the full expansion and contraction of the element due to the temperature change is effective in the operation of the thermostatic switch. In some thermostatic devices, due to the weight moved or strain imposed, the bimetallic element is distorted and the expansion or contraction is not effective until the strain imposedis overcome. In such previous devices no delicate adjustment can be secured, as such devices would only operate under influence of a very considerable temperature change, which defect is obviated by the general structure herein disclosed.

Having thus fully described my invention, what I claim is 1. A thermostatic switch comprising a support adapted to be turned on an axis,

a switch arm pivoted to the said support at a point below the axis thereof, a contact on each side of a vertical line passing through the axis of the support, the switch arm, on turning of the support on its axis, being unbalanced to fall by gravity to engage one or the other of the contacts depending upon the direction in which the support is turned,

and an element adapted through influence of temperature change to turn the support in one direction or the other.

2. A thermostatically controlled electric switch comprising a member mounted to turn freely upon an axis, an element adapted by expansion or contraction due to temperature change to turn the member in one direction or the other, a pair of contacts above the axis of the member on-opposite sides equi-distantly of a vertical line passing through the axis, a switch arm pivotally mountedon the member on the said vertical line below the axis, the upper end of the switch arm being weighted and adapted through the turning of the member to engage one or the other of the contacts, and an electric circuit for each contact closed by engagement of the switch arm therewith.

3. A thermostatically controlled electric switch comprising a hollow case mounted to turn upon an axis, the case being formed of two parts secured together to practically seal the interior to atmosphere, an element connected therewith and being of a character whereby, expansion or contraction thereof due to the temperature change may turn the case about its axis, a pair of contact members in the case above the axis and equi-distantly disposed on opposite sides of a vertical hne passing through the axis, a switch arm pivotally mounted on the said vertical line below the axis of the ease, and a circuit for each of the said contacts adapted to be closed upon engagement of the switch arm therewith, the turning of the case tending to unbalance the switch arm to fall by gravity against either contact.

4:. A thermostatically controlled electric switch comprising a stat-ionarily'supported shaft, a member rotatably mounted thereon, an element of spiral form having one end secured to the member and the other end adjustably secured relative to the shaft permitting the point of attachment of the element therewith to be turned about the axis of the shaft, the said rotatable member on the shaft havin therein above tie axis of the shaft, positioned equidistantly on opposite sides of a verticalline, a switch arm pivotally mounted on the said element at a point below the axis ofthe shaft, a supply circuit havin one side connected with the switch arm an the contacts each forming part of a circuit for an apparatus to be controlled, the expansion or contraction of the element tending-to turn the said member on the shaft'in one direction or the other to cause the switch arm to engage one or the other of the contacts.

5. A thermostatically cont-rolled electric switch comprising a stationarily supported shaft, a hollow case formed of two parts secured together mounted to be rotated ormoved longitudinally of the-shaft, an element of helical form having one end secured to the case, a rotatively adjustable member at the end of, the shaft to which the other end of the member is secured, a friction device tending to hold the adjustable member in set position, a pair of contact members in the case above the axis and positioned equidistantly upon opposite sides of a diametrical line of the case, a switch arm pivoted on the said diametrical line below, the axis of the shaft, said arm having a weighted upper end adapted to engage either of the said contacts, a circuit for the arm and the said contacts, the said arm being freely pivoted whereby turning of the case by the expansion or contraction of the element due to temperature change causes the arm to fall by gravity to engage either contact depending upon the direction the case is turned.

6. A thermostatic switch consisting of a support adapted to be freely turned on an axis, an unstable switch arm carried by the support, contacts with which the switch arm may engage on being unbalanced by the turning of the support in one direction or the other, and an element adapted by expansion or contraction to turn the support, the switch arm being so mounted that its extent of movement is in excess of the'movement of the support by said element.

a pair of spaced contacts 7 In a switch, a switch arm support free- 1y turnable on an axis, a switch arm pivoted on the support, the axis of the arm spaced from that of the support, a contact posi- 5 tioned to one side of the vertical center line of the support cngugcablc by the arm, and an element :uhtptcd by expansion or contraction due to temperature changes to turn the support on its axis to raise the switch arm past the vertical center line of the support. 10

In testimony whereof, I sign this spccification.

CLARENCE M. HOLLEY. 

